Observational evidence of the relationship between the tropical tropopause and tropical easterly jet streams over the Indian monsoon region

Mehta, Sanjay Kumar

doi:10.1002/asl.1230

Atmospheric Science Letters

2024

DOI: 10.1002/asl.1230

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Observational evidence of the relationship between the tropical tropopause and tropical easterly jet streams over the Indian monsoon region

Sanjay Kumar Mehta

Abstract: This paper presents the first quantitative relationship between the cold point tropopause (CPT) and tropical easterly jet (TEJ) using radiosonde observations over Gadanki (13.45° N, 79.2° E) during the Indian summer monsoon season 2006–2014. CPT and TEJ peak altitudes () show amalgams of two categories of variability on the day‐to‐day scale. In category1 occurs close to and they show in‐phase variation. While in Category2 occurs far apart from and they do not show any relationship. For Category1 and are … Show more

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Identification of the Asian summer monsoon anticyclone based on tropical easterly and subtropical westerly jets during active and break phases

Musaid,

Mehta,

Tegtmeier

et al. 2024

Intl Journal of Climatology

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The Asian summer monsoon anticyclone (ASMA) plays a vital role in the transport and redistribution of the tracers in the upper troposphere and lower stratosphere during transient monsoon conditions. The ASMA can be identified using various diagnostics such as winds and divergence, potential vorticity, the Montgomery stream function or geopotential height. Its representation based on the commonly‐used existing method that takes a climatological range of the geopotential height (GPH) at a given pressure level is not robust and fails in several circumstances. In this study, we propose a new GPH method to define the ASMA for the active and break phases of the monsoon based on the GPH values at the tropical easterly jet (TEJ) and subtropical westerly jet (STJ) locations. The proposed method compares the GPH values at the locations corresponding to the wind speed maxima of TEJ and STJ at 100 hPa with the maximum GPH at 100 hPa and selects the one with the minimum difference to define the ASMA extent. The same procedures were applied to obtain the ASMA extent at 150 hPa. The ASMA extents are obtained using the method proposed here and the existing fixed GPH method for the 30 active and 27 break phases from 2005 to 2023. The fixed GPH method provides a larger ASMA extent for 24 active and 21 break phases, which appears to be an unrealistic estimation compared to the proposed method. Our proposed method identifies the ASMA extent that is larger and centred around the Iranian side during the active phases while it is smaller and centred around the Tibetan side during the break phases. Furthermore, the minimum concentration of ozone (O3), and maximum concentrations of carbon monoxide (CO) and water vapour (H2O) are also found to be centred near the Iranian side during the active phases and on the Tibetan side during the break phases. The tracer concentrations are generally higher for CO, H2O and O3 during the active phase than in the break phase. Tracer concentrations within the ASMA extent using the fixed GPH method are higher for O3 while lesser for CO and H2O when compared to the proposed method.

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Identification of the Asian summer monsoon anticyclone based on tropical easterly and subtropical westerly jets during active and break phases

Musaid,

Mehta,

Tegtmeier

et al. 2024

Intl Journal of Climatology

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Thermal Characteristics of the Extreme Cases of Tropopause Over the Tropics

Purushotham,

Mehta,

Ali

et al. 2024

Intl Journal of Climatology

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The anomalous variability of extreme cases of the tropical tropopause provides insight into the stratosphere‐troposphere exchange process crucial for understanding climate change. The present study analyses the extreme variability of the tropopause and its thermal structure over the tropics using GPS radio occultation data over the period 2006–2019. The extremely cold and warm tropopauses and extremely high and low tropopauses are identified based on the cold point tropopause temperature and height, respectively, when their values exceed two standard deviations with respect to their climatological means. The analyses revealed frequent occurrence of extreme cases of tropopause over the Atlantic Ocean compared to the Western Pacific Ocean. Individually, extremely warm and low cases occur more frequently over the subtropics, while extremely cold and high cases occur frequently over the deep tropics. These extreme cases pose different thermal structures bounded within the extremely low and high tropopauses throughout the tropics. The height difference between the extremely high and low tropopause cases is wider over the Atlantic Ocean and adjoining areas compared to the western Pacific Ocean. The temperature difference between the extremely warm and cold tropopause cases is higher in the Atlantic, Central Pacific, and Indonesian regions compared to the American, Indian Ocean, and western Pacific Ocean regions. The relationship between the El Niño Southern Oscillation (ENSO) phases and extreme tropopause cases is also investigated which reveals a higher occurrence of extremely high tropopause cases during the El Niño phase while low tropopause cases during the La Niña phase. Our analysis also revealed the thermal patterns of the extreme cases characterising colder and sharper tropopause over the convective regions compared to subsidence regions.

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Characteristics of the Tropical Tropopause over Chennai (13.0° N, 80.06° E) in the Northeast Monsoon Region

Pooja,

Mehta,

Kakkanattu

et al. 2024

Pure Appl. Geophys.

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Observational evidence of the relationship between the tropical tropopause and tropical easterly jet streams over the Indian monsoon region

Cited by 5 publications

References 50 publications

Identification of the Asian summer monsoon anticyclone based on tropical easterly and subtropical westerly jets during active and break phases

Identification of the Asian summer monsoon anticyclone based on tropical easterly and subtropical westerly jets during active and break phases

Thermal Characteristics of the Extreme Cases of Tropopause Over the Tropics

Characteristics of the Tropical Tropopause over Chennai (13.0° N, 80.06° E) in the Northeast Monsoon Region

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